Clustering Switches

This chapter provides the concepts and procedures to create and manage Catalyst 3560 switch clusters.

Note This chapter focuses on Catalyst 3560 switch clusters. It also includes guidelines and limitations for clusters mixed with other cluster-capable Catalyst switches, but it does not provide complete descriptions of the cluster features for these other switches. For complete cluster information for a specific Catalyst platform, refer to the software configuration guide for that switch.

Note Configuring switch clusters is more easily done from the Cluster Management Suite (CMS) web-based interface than through the command-line interface (CLI). Therefore, information in this chapter focuses on using CMS to create a cluster. See "Getting Started with CMS," for additional information about switch clusters and the clustering options. For complete procedures about using CMS to configure switch clusters, refer to the online help. For the CLI cluster commands, refer to the switch command reference.

Understanding Switch Clusters

A switch cluster is a set of up to 16 connected, cluster-capable Catalyst switches that are managed as a single entity. The switches in the cluster use the switch clustering technology so that you can configure and troubleshoot a group of different Catalyst desktop switch platforms through a single IP address.

In a switch cluster, 1 switch must be the cluster command switch and up to 15 other switches can be cluster member switches. The total number of switches in a cluster cannot exceed 16 switches. The cluster command switch is the single point of access used to configure, manage, and monitor the cluster member switches. Cluster members can belong to only one cluster at a time.

The benefits of clustering switches include:

•Management of Catalyst switches regardless of their interconnection media and their physical locations. The switches can be in the same location, or they can be distributed across a Layer 2 or Layer 3 (if your cluster is using a Catalyst 3550, Catalyst 3560, or Catalyst 3750 switch as a Layer 3 router between the Layer 2 switches in the cluster) network.

Cluster members are connected to the cluster command switch according to the connectivity guidelines described in the "Automatic Discovery of Cluster Candidates and Members" section. This section includes management VLAN considerations for the Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL switches. For complete information about these switches in a switch-cluster environment, refer to the software configuration guide for that specific switch.

•Command-switch redundancy if a cluster command switch fails. One or more switches can be designated as standby cluster command switches to avoid loss of contact with cluster members. A cluster standby group is a group of standby cluster command switches.

•Management of a variety of Catalyst switches through a single IP address. This conserves on IP addresses, especially if you have a limited number of them. All communication with the switch cluster is through the cluster command switch IP address.

Refer to the release notes for the list of Catalyst switches eligible for switch clustering, including which ones can be cluster command switches and which ones can only be cluster member switches, and the required software versions.

•It is connected to the standby cluster command switches through the management VLAN and to the cluster member switches through a common VLAN.

Note If your switch cluster has a Catalyst 3560 switch, it should be the cluster command switch unless the cluster has a Catalyst 3750 switch or switch stack. If the switch cluster has a Catalyst 3750 switch or switch stack, that switch or switch stack must be the cluster command switch.

Standby Cluster Command Switch Characteristics

A standby cluster command switch must meet these requirements:

•It is running Cisco IOS Release 12.1(19)EA1 or later.

•It has an IP address.

•It has CDP version 2 enabled.

•It is connected to the command switch and to other standby command switches through its management VLAN.

•It is connected to all other cluster member switches (except the cluster command and standby command switches) through a common VLAN.

•It is redundantly connected to the cluster so that connectivity to cluster member switches is maintained.

•It is not a command or member switch of another cluster.

Note Standby cluster command switches must be the same type of switches as the cluster command switch. For example, if the cluster command switch is a Catalyst 3560 switch, the standby cluster command switches must also be Catalyst 3560 switches. Refer to the switch configuration guide of other cluster-capable switches for their requirements on standby cluster command switches.

Candidate Switch and Cluster Member Switch Characteristics

Candidate switches are cluster-capable switches that have not yet been added to a cluster. Cluster member switches are switches that have actually been added to a switch cluster. Although not required, a candidate or cluster member switch can have its own IP address and password (for related considerations, see the "IP Addresses" section and "Passwords" section).

To join a cluster, a candidate switch must meet these requirements:

•It is running cluster-capable software.

•It has CDP version 2 enabled.

•It is not a command or cluster member switch of another cluster.

•If a cluster standby group exists, it is connected to every standby cluster command switch through at least one common VLAN. The VLAN to each standby cluster command switch can be different.

•It is connected to the cluster command switch through at least one common VLAN.

Note Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL candidate and cluster member switches must be connected through their management VLAN to the cluster command switch and standby cluster command switches. For complete information about these switches in a switch-cluster environment, refer to the software configuration guide for that specific switch.

This requirement does not apply if you have a Catalyst 2970, Catalyst 3550, Catalyst 3560, or Catalyst 3750 cluster command switch. Candidate and cluster member switches can connect through any VLAN in common with the cluster command switch.

Planning a Switch Cluster

Anticipating conflicts and compatibility issues is a high priority when you manage several switches through a cluster. This section describes these guidelines, requirements, and caveats that you should understand before you create the cluster:

Refer to the release notes for the list of Catalyst switches eligible for switch clustering, including which ones can be cluster command switches and which ones can only be cluster member switches, and for the required software versions and browser and Java plug-in configurations.

Note Do not disable CDP on the cluster command switch, on cluster members, or on any cluster-capable switches that you might want a cluster command switch to discover. For more information about CDP, see "Configuring CDP."

Discovery Through CDP Hops

By using CDP, a cluster command switch can discover switches up to seven CDP hops away (the default is three hops) from the edge of the cluster. The edge of the cluster is where the last cluster member switches are connected to the cluster and to candidate switches. For example, cluster member switches 9 and 10 in Figure 5-1 are at the edge of the cluster.

You can set the number of hops the cluster command switch searches for candidate and cluster member switches by selecting Cluster > Hop Count. When new candidate switches are added to the network, the cluster command switch discovers them and adds them to the list of candidate switches.

In Figure 5-1, the cluster command switch has ports assigned to VLANs 16 and 62. The CDP hop count is three. The cluster command switch discovers switches 11, 12, 13, and 14 because they are within three hops from the edge of the cluster. It does not discover switch 15 because it is four hops from the edge of the cluster.

Figure 5-1 Discovery Through CDP Hops

Discovery Through Non-CDP-Capable and Noncluster-Capable Devices

If a cluster command switch is connected to a non-CDP-capable third-party hub (such as a non-Cisco hub), it can discover cluster-enabled devices connected to that third-party hub. However, if the cluster command switch is connected to a noncluster-capable Cisco device, it cannot discover a cluster-enabled device connected beyond the noncluster-capable Cisco device.

Figure 5-2 shows that the cluster command switch discovers the switch that is connected to a third-party hub. However, the cluster command switch does not discover the switch that is connected to a Catalyst 5000 switch.

Discovery Through Different VLANs

If the cluster command switch is a Catalyst 2970, Catalyst 3550, Catalyst 3560, or Catalyst 3750 switch, the cluster can have cluster member switches in different VLANs. As cluster member switches, they must be connected through at least one VLAN in common with the cluster command switch. The cluster command switch in Figure 5-3 has ports assigned to VLANs 9, 16, and 62 and therefore discovers the switches in those VLANs. It does not discover the switch in VLAN 50. It also does not discover the switch in VLAN 16 in the first column because the cluster command switch has no VLAN connectivity to it.

Discovery Through Different Management VLANs

Catalyst 2970, Catalyst 3550, Catalyst 3560, or Catalyst 3750 cluster command switches can discover and manage cluster member switches in different VLANs and different management VLANs. As cluster member switches, they must be connected through at least one VLAN in common with the cluster command switch. They do not need to be connected to the cluster command switch through their management VLAN. The default management VLAN is VLAN 1.

Note If the switch cluster has a Catalyst 3750 switch or switch stack, that switch or switch stack must be the cluster command switch.

The cluster command switch and standby command switch in Figure 5-4 (assuming they are Catalyst 2970, Catalyst 3550, Catalyst 3560, or Catalyst 3750 cluster command switches) have ports assigned to VLANs 9, 16, and 62. The management VLAN on the cluster command switch is VLAN 9. Each cluster command switch discovers the switches in the different management VLANs except these:

•Switches 7 and 10 (switches in management VLAN 4) because they are not connected through a common VLAN (meaning VLANs 62 and 9) with the cluster command switch

•Switch 9 because automatic discovery does not extend beyond a noncandidate device, which is switch 7

Discovery Through Routed Ports

If the cluster command switch has a routed port (RP) configured, it discovers only candidate and cluster member switches in the same VLAN as the routed port. For more information about routed ports, see the "Routed Ports" section.

The Layer 3 cluster command switch in Figure 5-5 can discover the switches in VLANs 9 and 62 but not the switch in VLAN 4. If the routed port path between the cluster command switch and cluster member switch 7 is lost, connectivity with cluster member switch 7 is maintained because of the redundant path through VLAN 9.

Figure 5-5 Discovery Through Routed Ports

Discovery of Newly Installed Switches

To join a cluster, the new, out-of-the-box switch must be connected to the cluster through one of its access ports. An access port (AP) carries the traffic of and belongs to only one VLAN. By default, the new switch and its access ports are assigned to VLAN 1.

When the new switch joins a cluster, its default VLAN changes to the VLAN of the immediately upstream neighbor. The new switch also configures its access port to belong to the VLAN of the immediately upstream neighbor.

The cluster command switch in Figure 5-6 belongs to VLANs 9 and 16. When new cluster-capable switches join the cluster:

•One cluster-capable switch and its access port are assigned to VLAN 9.

•The other cluster-capable switch and its access port are assigned to management VLAN 16.

Figure 5-6 Discovery of Newly Installed Switches

HSRP and Standby Cluster Command Switches

The switch supports Hot Standby Router Protocol (HSRP) so that you can configure a group of standby cluster command switches. Because a cluster command switch manages the forwarding of all communication and configuration information to all the cluster member switches, we strongly recommend the following:

•For a cluster command switch stack, a standby cluster command switch is necessary if the entire switch stack fails. However, if only the stack master in the command switch stack fails, the switch stack elects a new stack master and resumes its role as the cluster command switch stack.

•For a cluster command switch that is a standalone switch, configure a standby cluster command switch to take over if the primary cluster command switch fails.

Note If your switch cluster has a Catalyst 3560 switch, it should be the cluster command switch unless the cluster has a Catalyst 3750 switch or switch stack. If the switch cluster has a Catalyst 3750 switch or switch stack, that switch or switch stack must be the cluster command switch.

Note The cluster standby group is an HSRP group. Disabling HSRP disables the cluster standby group.

The switches in the cluster standby group are ranked according to HSRP priorities. The switch with the highest priority in the group is the active cluster command switch (AC). The switch with the next highest priority is the standby cluster command switch (SC). The other switches in the cluster standby group are the passive cluster command switches (PC). If the active cluster command switch and the standby cluster command switch become disabled at the same time, the passive cluster command switch with the highest priority becomes the active cluster command switch. For the limitations to automatic discovery, see the "Automatic Recovery of Cluster Configuration" section. For information about changing HSRP priority values, see the "Configuring HSRP Priority" section. The HSRP standby priority interface configuration commands are the same for changing the priority of cluster standby group members and router-redundancy group members.

Note The HSRP standby hold time interval should be greater than or equal to three times the hello time interval. The default HSRP standby hold time interval is 10 seconds. The default HSRP standby hello time interval is 3 seconds. For more information about the standby hold time and standby hello time intervals, see the "Configuring HSRP Authentication and Timers" section.

Virtual IP Addresses

You need to assign a unique virtual IP address and group number and name to the cluster standby group. This information must be configured on a specific VLAN or routed port on the active cluster command switch. The active cluster command switch receives traffic destined for the virtual IP address. To manage the cluster, you must access the active cluster command switch through the virtual IP address, not through the command-switch IP address. This is in case the IP address of the active cluster command switch is different from the virtual IP address of the cluster standby group.

If the active cluster command switch fails, the standby cluster command switch assumes ownership of the virtual IP address and becomes the active cluster command switch. The passive switches in the cluster standby group compare their assigned priorities to decide the new standby cluster command switch. The passive standby switch with the highest priority then becomes the standby cluster command switch. When the previously active cluster command switch becomes active again, it resumes its role as the active cluster command switch, and the current active cluster command switch becomes the standby cluster command switch again. For more information about IP address in switch clusters, see the "IP Addresses" section.

Other Considerations for Cluster Standby Groups

These requirements also apply:

•Standby cluster command switches must be the same type of switches as the cluster command switch. For example, if the cluster command switch is a Catalyst 3560 switch, the standby cluster command switches must also be Catalyst 3560 switches. Refer to the switch configuration guide of other cluster-capable switches for their requirements on standby cluster command switches.

If your switch cluster has a Catalyst 3560 switch, it should be the cluster command switch unless the cluster has a Catalyst 3750 switch or switch stack. If the switch cluster has a Catalyst 3750 switch or switch stack, that switch or switch stack must be the cluster command switch.

•Only one cluster standby group can be assigned to a cluster. You can have more than one router-redundancy standby group.

An HSRP group can be both a cluster standby group and a router-redundancy group. However, if a router-redundancy group becomes a cluster standby group, router redundancy becomes disabled on that group. You can re-enable it by using the CLI. For more information about HSRP and router redundancy, see "Configuring HSRP."

•All standby-group members must be members of the cluster.

Note There is no limit to the number of switches that you can assign as standby cluster command switches. However, the total number of switches in the cluster—which would include the active cluster command switch, standby-group members, and cluster member switches—cannot be more than 16.

•Each standby-group member (Figure 5-7) must be connected to the cluster command switch through the same VLAN. In this example, the cluster command switch and standby cluster command switches are Catalyst 2970, Catalyst 3550, Catalyst 3560, or Catalyst 3750 cluster command switches. Each standby-group member must also be redundantly connected to each other through at least one VLAN in common with the switch cluster.

Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL cluster member switches must be connected to the cluster standby group through their management VLANs. For more information about VLANs in switch clusters, see these sections:

Figure 5-7 VLAN Connectivity between Standby-Group Members and Cluster Members

Automatic Recovery of Cluster Configuration

The active cluster command switch continually forwards cluster-configuration information (but not device-configuration information) to the standby cluster command switch. This ensures that the standby cluster command switch can take over the cluster immediately after the active cluster command switch fails.

Automatic discovery has these limitations:

•This limitation applies only to clusters that have Catalyst 2950, Catalyst 3550, Catalyst 3560, and Catalyst 3750 command and standby cluster command switches: If the active cluster command switch and standby cluster command switch become disabled at the same time, the passive cluster command switch with the highest priority becomes the active cluster command switch. However, because it was a passive standby cluster command switch, the previous cluster command switch did not forward cluster-configuration information to it. The active cluster command switch only forwards cluster-configuration information to the standby cluster command switch. You must therefore rebuild the cluster.

•This limitation applies to all clusters: If the active cluster command switch fails and there are more than two switches in the cluster standby group, the new cluster command switch does not discover any Catalyst 1900, Catalyst 2820, and Catalyst 2916M XL cluster member switches. You must re-add these cluster member switches to the cluster.

•This limitation applies to all clusters: If the active cluster command switch fails and becomes active again, it does not discover any Catalyst 1900, Catalyst 2820, and Catalyst 2916M XL cluster member switches. You must again add these cluster member switches to the cluster.

When the previously active cluster command switch resumes its active role, it receives a copy of the latest cluster configuration from the active cluster command switch, including members that were added while it was down. The active cluster command switch sends a copy of the cluster configuration to the cluster standby group.

IP Addresses

You must assign IP information to a cluster command switch. You can assign more than one IP address to the cluster command switch, and you can access the cluster through any of the command-switch IP addresses. If you configure a cluster standby group, you must use the standby-group virtual IP address to manage the cluster from the active cluster command switch. Using the virtual IP address ensures that you retain connectivity to the cluster if the active cluster command switch fails and that a standby cluster command switch becomes the active cluster command switch.

If the active cluster command switch fails and the standby cluster command switch takes over, you must either use the standby-group virtual IP address or any of the IP addresses available on the new active cluster command switch to access the cluster.

You can assign an IP address to a cluster-capable switch, but it is not necessary. A cluster member switch is managed and communicates with other cluster member switches through the command-switch IP address. If the cluster member switch leaves the cluster and it does not have its own IP address, you then must assign IP information to it to manage it as a standalone switch.

Note Changing the cluster command switch IP address ends your CMS session on the switch. Restart your CMS session by entering the new IP address in the browser Location field (Netscape Communicator) or Address field (Internet Explorer), as described in the release notes.

Host Names

You do not need to assign a host name to either a cluster command switch or an eligible cluster member. However, a host name assigned to the cluster command switch can help to identify the switch cluster. The default host name for the switch is Switch.

If a switch joins a cluster and it does not have a host name, the cluster command switch appends a unique member number to its own host name and assigns it sequentially as each switch joins the cluster. The number means the order in which the switch was added to the cluster. For example, a cluster command switch named eng-cluster could name the fifth cluster member eng-cluster-5.

If a switch has a host name, it retains that name when it joins a cluster. It retains that host name even after it leaves the cluster.

If a switch received its host name from the cluster command switch, was removed from a cluster, was then added to a new cluster, and kept the same member number (such as 5), the old host name (such as eng-cluster-5) is overwritten with the host name of the cluster command switch in the new cluster (such as mkg-cluster-5). If the switch member number changes in the new cluster (such as 3), the switch retains the previous name (eng-cluster-5).

Passwords

You do not need to assign passwords to an individual switch if it will be a cluster member. When a switch joins a cluster, it inherits the command-switch password and retains it when it leaves the cluster. If no command-switch password is configured, the cluster member switch inherits a null password. Cluster member switches only inherit the command-switch password.

If you change the member-switch password to be different from the command-switch password and save the change, the switch is not manageable by the cluster command switch until you change the member-switch password to match the command-switch password. Rebooting the member switch does not revert the password back to the command-switch password. We recommend that you do not change the member-switch password after it joins a cluster.

For password considerations specific to the Catalyst 1900 and Catalyst 2820 switches, refer to the installation and configuration guides for those switches.

SNMP Community Strings

A cluster member switch inherits the command-switch first read-only (RO) and read-write (RW) community strings with @esN appended to the community strings:

•command-switch-readonly-community-string@esN, where N is the member-switch number.

•command-switch-readwrite-community-string@esN, where N is the member-switch number.

If the cluster command switch has multiple read-only or read-write community strings, only the first read-only and read-write strings are propagated to the cluster member switch.

The switches support an unlimited number of community strings and string lengths. For more information about SNMP and community strings, see "Configuring SNMP."

For SNMP considerations specific to the Catalyst 1900 and Catalyst 2820 switches, refer to the installation and configuration guides specific to those switches.

TACACS+ and RADIUS

Inconsistent authentication configurations in switch clusters cause CMS to continually prompt for a user name and password. If Terminal Access Controller Access Control System Plus (TACACS+) is configured on a cluster member, it must be configured on all cluster members. Similarly, if Remote Authentication Dial-In User Service (RADIUS) is configured on a cluster member, it must be configured on all cluster members. Further, the same switch cluster cannot have some members configured with TACACS+ and other members configured with RADIUS.

Access Modes in CMS

If your cluster has these cluster member switches running earlier software releases and if you have read-only access to these cluster member switches, some configuration windows for those switches display incomplete information:

LRE Profiles

A configuration conflict occurs if a switch cluster has Long-Reach Ethernet (LRE) switches that use both private and public profiles. If one LRE switch in a cluster is assigned a public profile, all LRE switches in that cluster must have that same public profile. Before you add an LRE switch to a cluster, make sure that you assign it the same public profile used by other LRE switches in the cluster.

A cluster can have a mix of LRE switches that use different private profiles.

Availability of Switch-Specific Features in Switch Clusters

The menu bar on the cluster command switch displays all options available from the switch cluster. Therefore, features specific to a cluster member switch are available from the command-switch menu bar. For example, Device > LRE Profile appears in the command-switch menu bar when at least one Catalyst 2900 LRE XL switch is in the cluster.

Creating a Switch Cluster

Using CMS to create a cluster is easier than using the CLI commands. This section provides this information:

This section assumes you have already connected the switches, as described in the switch hardware installation guide, and followed the guidelines described in the "Planning a Switch Cluster" section.

Note Refer to the release notes for the list of Catalyst switches eligible for switch clustering, including which ones can be cluster command switches and which ones can only be cluster member switches, and for the required software versions and browser and Java plug-in configurations.

Note If your switch cluster has a Catalyst 3560 switch, it should be the cluster command switch unless the cluster has a Catalyst 3750 switch or switch stack. If the switch cluster has a Catalyst 3750 switch or switch stack, that switch or switch stack must be the cluster command switch.

You can enable a cluster command switch, name the cluster, and assign an IP address and a password to the cluster command switch when you run the setup program during initial switch setup. For information about using the setup program, refer to the release notes.

If you did not enable a cluster command switch during initial switch setup, launch Device Manager from a command-capable switch, and select Cluster > Create Cluster. Enter a cluster number (the default is 0), and use up to 31 characters to name the cluster (Figure 5-8). Instead of using CMS to enable a cluster command switch, you can use the cluster enable global configuration command.

•Select Cluster > Add to Cluster, select a candidate switch from the list, click Add, and click OK. To add more than one candidate switch, press Ctrl, and make your choices, or press Shift, and choose the first and last switch in a range.

•Display the Topology view, right-click a candidate-switch icon, and select Add to Cluster (Figure 5-10). In the Topology view, candidate switches are cyan, and cluster member switches are green. To add more than one candidate switch, press Ctrl, and left-click the candidates that you want to add.

Instead of using CMS to add members to the cluster, you can use the cluster member global configuration command from the cluster command switch. Use the password option in this command if the candidate switch has a password.

You can select 1 or more switches as long as the total number of switches in the cluster does not exceed 16 (this includes the cluster command switch). When a cluster has 16 members, the Add to Cluster option is not available for that cluster. In this case, you must remove a cluster member switch before adding a new one.

If a password has been configured on a candidate switch, you are prompted to enter it before it can be added it to the cluster. If the candidate switch does not have a password, any entry is ignored.

If multiple candidates switches have the same password, you can select them as a group, and add them at the same time.

If a candidate switch in the group has a password different from the group, only that specific candidate switch is not added to the cluster.

When a candidate switch joins a cluster, it inherits the command-switch password. For more information about setting passwords, see the "Passwords" section.

Instead of using CMS to add switches to a standby group and to bind the standby group to a cluster, you can use the standby ip, the standby name, and the standby priority interface configuration commands and the cluster standby group global configuration command.

Note Standby cluster command switches must be the same type of switches as the cluster command switch. For example, if the cluster command switch is a Catalyst 3560 switch, the standby cluster command switches must also be Catalyst 3560 switches. Refer to the switch configuration guide of other cluster-capable switches for their requirements on standby cluster command switches.

These abbreviations are appended to the switch host names in the Standby Command Group list to show their eligibility or status in the cluster standby group:

•AC—Active cluster command switch

•SC—Standby cluster command switch

•PC—Member of the cluster standby group but not the standby cluster command switch

•HC—Candidate switch that can be added to the cluster standby group

•CC—Cluster command switch when HSRP is disabled

You must enter a virtual IP address for the cluster standby group. This address must be in the same subnet as the IP addresses of the switch. The group number must be unique within the IP subnet. It can be from 0 to 255, and the default is 0. The group name can have up to 31 characters.

The Standby Command Configuration window uses the default values for the preempt and name commands that you have set by using the CLI. If you use this window to create the standby group, all switches in the group have the preempt command enabled. You must also provide a name for the group.

Note The HSRP standby hold time interval should be greater than or equal to three times the hello time interval. The default HSRP standby hold time interval is 10 seconds. The default HSRP standby hello time interval is 3 seconds. For more information about the standby hold time and standby hello time intervals, see the "Configuring HSRP Authentication and Timers" section.

Figure 5-11 Standby Command Configuration Window

Verifying a Switch Cluster

When you finish adding cluster members, follow these steps to verify the cluster:

Step 1 Enter the cluster command switch IP address in the browser Location field (Netscape Communicator) or Address field (Microsoft Internet Explorer) to access all switches in the cluster.

Step 2 Enter the command-switch password.

Step 3 Select View > Topology to display the cluster topology and to view link information (Figure 3-8). For complete information about the Topology view, including descriptions of the icons, links, and colors, see the "Topology View" section.

Step 4 Select Reports > Inventory to display an inventory of the switches in the cluster (Figure 5-12).

Instead of using CMS to verify the cluster, you can use the show cluster members user EXEC command from the cluster command switch or use the show cluster user EXEC command from the cluster command switch or from a cluster member switch.

Figure 5-12 Inventory Window

If you lose connectivity with a cluster member switch or if a cluster command switch fails, see the cluster-related recovery procedures in "Troubleshooting."

For more information about creating and managing clusters, refer to the online help. For information about the cluster commands, refer to the switch command reference.

Using the CLI to Manage Switch Clusters

You can configure cluster member switches from the CLI by first logging into the cluster command switch. Enter the rcommand user EXEC command and the cluster member switch number to start a Telnet session (through a console or Telnet connection) and to access the cluster member switch CLI. The command mode changes, and the Cisco IOS commands operate as usual. Enter the exit privileged EXEC command on the cluster member switch to return to the command-switch CLI.

This example shows how to log into member-switch 3 from the command-switch CLI:

switch# rcommand 3

If you do not know the member-switch number, enter the show cluster members privileged EXEC command on the cluster command switch. For more information about the rcommand command and all other cluster commands, refer to the switch command reference.

The Telnet session accesses the member-switch CLI at the same privilege level as on the cluster command switch. The Cisco IOS commands then operate as usual. For instructions on configuring the switch for a Telnet session, see the "Disabling Password Recovery" section.

Catalyst 1900 and Catalyst 2820 CLI Considerations

If your switch cluster has Catalyst 1900 and Catalyst 2820 switches running standard edition software, the Telnet session accesses the management console (a menu-driven interface) if the cluster command switch is at privilege level 15. If the cluster command switch is at privilege level 1 to 14, you are prompted for the password to access the menu console.

•If the command-switch privilege level is 1 to 14, the cluster member switch is accessed at privilege level 1.

•If the command-switch privilege level is 15, the cluster member switch is accessed at privilege level 15.

Note The Catalyst 1900 and Catalyst 2820 CLI is available only on switches running Enterprise Edition Software.

For more information about the Catalyst 1900 and Catalyst 2820 switches, refer to the installation and configuration guides for those switches.

Using SNMP to Manage Switch Clusters

When you first power on the switch, SNMP is enabled if you enter the IP information by using the setup program and accept its proposed configuration. If you did not use the setup program to enter the IP information and SNMP was not enabled, you can enable it as described in the "Configuring SNMP" section. On Catalyst 1900 and Catalyst 2820 switches, SNMP is enabled by default.

When you create a cluster, the cluster command switch manages the exchange of messages between cluster member switches and an SNMP application. The cluster software on the cluster command switch appends the cluster member switch number (@esN, where N is the switch number) to the first configured read-write and read-only community strings on the cluster command switch and propagates them to the cluster member switch. The cluster command switch uses this community string to control the forwarding of gets, sets, and get-next messages between the SNMP management station and the cluster member switches.

Note When a cluster standby group is configured, the cluster command switch can change without your knowledge. Use the first read-write and read-only community strings to communicate with the cluster command switch if there is a cluster standby group configured for the cluster.

If the cluster member switch does not have an IP address, the cluster command switch redirects traps from the cluster member switch to the management station, as shown in Figure 5-13. If a cluster member switch has its own IP address and community strings, the cluster member switch can send traps directly to the management station, without going through the cluster command switch.

If a cluster member switch has its own IP address and community strings, they can be used in addition to the access provided by the cluster command switch. For more information about SNMP and community strings, see "Configuring SNMP."